The Common Internet File System (CIFS) Protocol is a cross-platform, transport-independent protocol that provides a mechanism for client systems to use file and print services made available by server systems over a network.
CIFS is a dialect of the Server Message Block (SMB) protocol, which was originally developed by IBM Corporation and then further enhanced by Microsoft, IBM, Intel, 3Com, and others. There are several dialects of SMB. A standard for the SMB protocol, covering dialects prior to CIFS, was published by X/Open (now The Open Group) as [XOPEN-SMB].
The meaning of the term "CIFS" has changed since it was first introduced. It was originally used to indicate a proposed standard version of SMB based upon the design of the Windows NT 4.0 operating system and Windows 2000 operating system implementations. In some references, "CIFS" has been used as a name for the SMB protocol in general (all dialects) and, additionally, the suite of protocols that support and include SMB. In this document, the term "CIFS" is used specifically to identify the Windows NT LAN Manager (NTLM) dialect of SMB as designed for use with Windows: in particular, Windows NT Server 3.51 operating system and Windows NT Server 4.0 operating system, Windows NT Workstation 4.0 operating system, and Microsoft Windows 98 operating system.
This document defines the protocol as it was designed for Windows NT operating system. It also specifies the behaviors of Windows NT and Windows 98, with respect to optional behavior, and documents known errors and variances in implementation. Changes and enhancements made to the SMB protocol are documented in [MS-SMB].
Sections 1.8, 2, and 3 of this specification are normative and can contain the terms MAY, SHOULD, MUST, MUST NOT, and SHOULD NOT as defined in RFC 2119. Sections 1.5 and 1.9 are also normative but cannot contain those terms. All other sections and examples in this specification are informative.